A cardiac rhythm management device can electrostimulate excitable heart tissue cells adjacent to the electrode of the lead coupled to the rhythm management device. Response to myocardial stimulation or “capture” is a function of the positive and negative charges found in each myocardial cell within the heart. A cardiac rhythm management device causes a depolarization or evokes a response when the energy of the pacing or other electrostimulus delivered to the myocardium exceeds a threshold value. This threshold value, referred to as the capture threshold, represents the amount of electrical energy that will alter the permeability of the myocardial cells to thereby initiate cell depolarization. If the energy of the pacing stimulus does not exceed the capture threshold, then the permeability of the myocardial cells will not be altered and thus no depolarization can result. If, on the other hand, the energy of the pacing stimulus exceeds the capture threshold, then the permeability of the myocardial cells will be altered such that depolarization can result.